WO2023113160A1 - Optical film and display device comprising same - Google Patents

Abstract

The present invention provides an optical film and a display device comprising same, the optical film comprising a light-transmissive substrate, having a yellowness of 5.0 or less before a light resistance test, and having a color change (ΔE*_ab) of 3.5 or less after the light resistance test.

Description

Optical film and display device including the same

The present invention relates to an optical film and a display device including the same.

Recently, due to thinning, lightening, and flexibility of display devices, the use of an optical film containing a polymer resin instead of glass as a cover window has been studied. In order for an optical film to be used as a cover window of a display device, it must have excellent optical and mechanical properties.

On the other hand, the optical film containing a polymer resin has a problem in that the initial yellowness is high or the color of the optical film changes as time passes and is exposed to light.

Therefore, it is required to develop a film having excellent mechanical properties such as insolubility, chemical resistance and heat resistance, and excellent optical properties such as light resistance.

Accordingly, one embodiment of the present invention is to provide an optical film having excellent light resistance.

In addition, another embodiment of the present invention is to provide a display device including an optical film having excellent light resistance.

An embodiment of the present invention provides an optical film, including a light-transmitting substrate, having a yellowness of 5.0 or less before the light fastness test and having a color change (ΔE* _ab ) of 3.5 or less after the light fastness test.

The light resistance test was conducted for 300 hours under the conditions of a Daylight filter, 12kW 0.8W/m2 @420nm, 30 ^o C/30RH% Chamber, and 55 ^o C Black Panel using a Xenon lamp, and the color change ( ΔE* _ab ) is calculated by Equation 1 below.

<Formula 1>

ΔE* _ab = [(ΔL*) ² + (Δa*) ² +(Δb*) ² ] ^1/2

In Equation 1, ΔL* is the L* difference before and after the light fastness test, Δa* is the a* difference before and after the light fastness test, and Δb* is the b* difference before and after the light fastness test.

The light-transmitting substrate may include a polymer resin; And a malonate-based (Malonate) UV absorber; may include.

When the ultraviolet absorber is dissolved in DAMc at a concentration of 0.001 wt%, the maximum absorbance in the UVA region (315 to 400 nm) may be 0.45 or more.

The ultraviolet absorber may include a compound represented by Chemical Formula 2 below.

<Formula 2>

In Formula 2, R ¹ , R ² , R ³ and R ⁴ are each independently hydrogen; halogen element; phenyl group; Or a C1~C10 linear, branched or alicyclic alkyl group; Y is a divalent aromatic or heteroorganic group having 6 to 40 carbon atoms, and a hydrogen atom in the organic group included in Formula 2 is a halogen element; hydrocarbon group; a halogen-substituted hydrocarbon group; Alternatively, it may be substituted by a halogen element, an oxygen or nitrogen substituted hydrocarbon group.

The UV absorber may include Tetraethyl 2,2'-(1,4-phenylenedimethylidyne)bismalonate.

The light-transmitting substrate may include 1 to 10 parts by weight of the ultraviolet absorber based on 100 parts by weight of the polymer resin.

The polymer resin may include at least one of an imide repeating unit and an amide repeating unit.

The optical film may have a light transmittance of 88.5% or more after a light fastness test, and a haze of 1.0 or less after a light fastness test.

Another embodiment of the present invention, the display panel; and the optical film disposed on the display panel.

According to one embodiment of the present invention, it is possible to provide an optical film having excellent light resistance in the UVA region (315 to 400 nm).

According to another embodiment of the present invention, a display device including an optical film having excellent light resistance in the UVA region (315 to 400 nm) can be provided.

1 is a cross-sectional view of an optical film 100 according to an embodiment of the present invention.

2 is a cross-sectional view of the optical film 101 further including a primer layer 120.

3 is a cross-sectional view of the optical film 102 further including a hard coat layer 130.

4 is a cross-sectional view of a portion of a display device 200 according to another embodiment of the present invention.

5 is an enlarged cross-sectional view of part “P” in FIG. 4 .

Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are only presented for illustrative purposes to help a clear understanding of the present invention, and do not limit the scope of the present invention.

Since the shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, the present invention is not limited to those shown in the drawings. Like elements may be referred to by like reference numerals throughout the specification. In describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

When 'includes', 'has', 'consists', etc. mentioned in this specification is used, other parts may be added unless the expression 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise. In addition, in interpreting the components, even if there is no separate explicit description, it is interpreted as including the error range.

In the case of a description of a positional relationship, for example, 'on top of', 'on top of', 'at the bottom of', 'next to', etc. Or, unless the word 'directly' is used, one or more other parts may be located between the two parts.

The spatially relative terms "below, beneath", "lower", "above", "upper", etc., refer to one element or component as shown in the drawing. It can be used to easily describe the correlation between and other elements or components. Spatially relative terms should be understood as encompassing different orientations of elements in use or operation in addition to the orientations shown in the figures. For example, when flipping elements shown in the figures, elements described as “below” or “beneath” other elements may be placed “above” the other elements. Thus, the exemplary term “below” may include directions of both below and above. Likewise, the exemplary terms "above" or "above" can include both directions of up and down.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal precedence relationship is described in terms of 'after', 'following', 'next to', 'before', etc. Unless the expression is used, non-continuous cases may also be included.

Although first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another. Therefore, the first component mentioned below may also be the second component within the technical spirit of the present invention.

The term “at least one” should be understood to include all possible combinations from one or more related items. For example, "at least one of the first item, the second item, and the third item" means not only the first item, the second item, or the third item, but also two of the first item, the second item, and the third item. It may mean a combination of all items that can be presented from one or more.

Each feature of the various embodiments of the present invention can be partially or entirely combined or combined with each other, technically various interlocking and driving are possible, and each embodiment can be implemented independently of each other or can be implemented together in a related relationship. may be

*35 Prior to describing the present invention in detail below, it should be understood that the terms used herein are only for describing specific embodiments and are not limited only by the scope of the appended claims. All technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art, unless otherwise specified.

In addition, in interpreting the terms or words used in the following specification and claims, the inventor must be able to properly define the concept of the term in order to explain his or her invention in the best way. It should not be construed as being limited to or limited to dictionary meanings, and should be interpreted as meanings and concepts corresponding to the technical spirit of the present invention as described in the present specification.

An embodiment of the present invention provides an optical film 100 . 1 is a cross-sectional view of an optical film 100 according to an embodiment of the present invention.

As shown in FIG. 1 , an optical film 100 according to an embodiment of the present invention includes a light-transmitting substrate 110 .

The optical film 100 according to an embodiment of the present invention has a yellowness of 5.0 or less before the light fastness test, and a color change (ΔE* _ab ) of 3.5 or less after the light fastness test.

Yellowness before the light fastness test can be measured using a spectrophotometer. Specifically, yellowness of the optical film may be measured using a spectrophotometer according to standard ASTM E313, for example, a spectrophotometer manufactured by KONICA MINOLTA (model name: CM-3700D).

The light resistance test is performed using a Xenon lamp, for example, ATLAS' SUNTEST XXL + device, Daylight filter, 12kW 0.8W/m2 @420nm, 30 ^o C/30RH% Chamber, 55 ^o C Black Performed for 300 hours under panel conditions, and the color change (ΔE* _ab ) is calculated by the following formula 1.

<Formula 1>

ΔE* _ab = [(ΔL*) ² + (Δa*) ² + (Δb*) ² ] ^1/2

In Equation 1, ΔL* is the L* difference before and after the light fastness test, Δa* is the a* difference before and after the light fastness test, and Δb* is the b* difference before and after the light fastness test.

L*, a*, and b* of the optical film 100 before the light fastness test may be measured using a color difference meter. Specifically, the optical film 100 was measured using a color difference meter, for example, KONICA MINOLTA's color difference meter (model name: CM-3600A), using a D65 light source, viewing angle of 2 °, and L*, a*, b* in transmission mode. is measured three times, respectively, and average values of L*, a*, and b* measured three times are calculated to be L*, a*, and b* of the optical film 100. L*, a*, b* after the light fastness test can be measured by the same method as the L*, a*, b* measurement method before the light fastness test.

When the yellowness of the optical film 100 is 5.0 or less before the light fastness test and the color change (ΔE* _ab ) after the light fastness test is 3.5 or less, the optical film 100 has excellent visibility and light fastness, particularly UV light fastness, and thus a display device. Suitable for use as a cover window for Since the polymer resin included in the light-transmitting substrate 110 of the optical film 100 has a large amount of aromatic rings, color change of the optical film 100 occurs when exposed to ultraviolet (UV) wavelength light for a long time. do. Accordingly, as time passes, color reproducibility and sharpness of the optical film 100 decrease, thereby reducing visibility. On the other hand, since the optical film 100 having excellent UV light resistance shows little color change even when exposed to ultraviolet (UV) wavelength light, the lifespan of the cover window of the display device may be increased.

The light transmissive substrate 110 according to an embodiment of the present invention may include a polymer resin and an ultraviolet absorber.

The polymer resin has excellent bending properties and impact resistance, and is suitable for use as a cover window of a flexible display device. The polymer resin may be included in various shapes and forms, such as a solid powder form in a film, a form dissolved in a solution, and a matrix form solidified after dissolving in a solution. And all can be seen as the same as the polymer resin of the present invention. In general, the polymer resin in the film may be present in the form of a matrix in which a polymer resin solution is applied and then dried and solidified.

The polymer resin according to an embodiment of the present invention may be any light-transmitting resin. For example, cycloolefin-based derivatives, cellulose-based polymers, ethylene-vinyl acetate-based copolymers, polyester-based polymers, polystyrene-based polymers, polyamide-based polymers, polyamide-imide-based polymers, polyetherimide-based polymers, polyacrylic-based polymers, Polyimide polymer, polyethersulfone polymer, polysulfone polymer, polyethylene polymer, polypropylene polymer, polymethylpentene polymer, polyvinyl chloride polymer, polyvinylidene chloride polymer, polyvinyl alcohol polymer, Polyvinyl acetal polymer, polyether ketone polymer, polyether ether ketone polymer, polymethyl methacrylate polymer, polyethylene terephthalate polymer, polybutylene terephthalate polymer, polyethylene naphthalate polymer, polycarbonate polymer It may include at least one selected from polymers, polyurethane-based polymers, and epoxy-based polymers. Preferably, the polymer resin according to an embodiment of the present invention may include at least one of a polyimide-based polymer, a polyamide-based polymer, and a polyamide-imide-based polymer. In particular, polyimide-based polymers, polyamide-based polymers, and polyamide-imide-based polymers have excellent optical properties such as light transmittance and haze as well as physical properties such as thermal properties, hardness, abrasion resistance, and flexibility, and thus cover windows of display devices. It is preferable that at least one of a polyimide-based polymer, a polyamide-based polymer, and a polyamide-imide-based polymer is included as the light-transmitting substrate 110 of the optical film 100 used as the . However, the present invention is not limited thereto.

According to an embodiment of the present invention, the light-transmitting substrate 110 may include a polymer resin including at least one of an imide repeating unit and an amide repeating unit. In the present invention, the imide repeating unit refers to a repeating unit generated by reacting a diamine-based compound and a dianhydride-based compound and imidating, and the amide repeating unit is a repeating unit generated by reacting a diamine-based compound and a dicarbonyl-based compound. say unit The light-transmitting substrate 110 may be any one of a polyimide-based substrate, a polyamide-based substrate, and a polyamide-imide-based substrate. However, one embodiment of the present invention is not limited thereto, and any substrate having light transmission may be the light transmission substrate 110 according to one embodiment of the present invention.

According to one embodiment of the present invention, the light-transmitting substrate 110 may include a UV absorber. The ultraviolet absorber may include a malonate compound. That is, the light-transmitting substrate 110 according to an embodiment of the present invention may include a malonate-based UV absorber.

The malonate-based compound of the present invention is a compound containing a malonate substituent, and the malonate substituent has a structure represented by Formula 1 below. That is, the malonate-based compound refers to a compound having a structure represented by Formula 1 below.

<Formula 1>

In Formula 1, R ¹ and R ² are each independently hydrogen; halogen element; phenyl group; or a C1~C10 linear, branched or alicyclic alkyl group;

The malonate compound minimizes the increase in the initial yellowness of the optical film 100 and has an excellent effect of improving the light resistance of the optical film 100, so when included as an ultraviolet absorber, the optical film 100 Color change upon exposure to light can be minimized.

According to one embodiment of the present invention, when the UV absorber is dissolved in DAMc at a concentration of 0.001 wt%, the maximum absorbance in the UVA region (315 to 400 nm) may be 0.45 or more.

The maximum absorbance in the UVA region (315 to 400 nm) of the UV absorber can be measured using a UV spectrophotometer. Specifically, the UV absorber is dissolved in DMAc (N, N-Dimethylacetamide) at a concentration of 0.001 wt%, and an ultraviolet spectrometer, for example, Shimadzu's ultraviolet spectrometer (model name: UV-1800) is used to measure the UVA region (315-400 nm). ), and the maximum value of the absorbance measured in the UVA region (315 to 400 nm) is the maximum absorbance in the UVA region (315 to 400 nm) of the UV absorber.

When the maximum absorbance in the UVA region (315 to 400 nm) of the ultraviolet absorber is 0.45 or more, the initial yellowness of the optical film 100 is minimized and the light resistance is improved so that the initial yellowness is 5.0 or less, and in addition, the light resistance test is performed. After that, the color change (ΔE* _ab ) may be 3.5 or less.

According to one embodiment of the present invention, the ultraviolet absorber may include at least two or more structures represented by Formula 1 above. That is, the UV absorber may include at least two or more malonate substituents.

When the UV absorber includes two or more malonate substituents, the absorbance of the UV absorber increases, and the maximum absorbance in the UVA region (315 to 400 nm) may be 0.45 or more.

According to one embodiment of the present invention, the ultraviolet absorber may include a compound represented by Chemical Formula 2 below.

<Formula 2>

*65 In Formula 2, R ¹ , R ² , R ³ and R ⁴ are each independently hydrogen; halogen element; phenyl group; Or a C1~C10 linear, branched or alicyclic alkyl group; Y is a divalent aromatic organic group or heterocyclic organic group having 6 to 40 carbon atoms, and a hydrogen atom in the organic group included in Formula 2 is a halogen element; hydrocarbon group; a halogen-substituted hydrocarbon group; Alternatively, it may be substituted by a halogen element, an oxygen or nitrogen substituted hydrocarbon group.

In Formula 2, Y may include, for example, a structure represented by any one of the structural formulas represented by Formula 3 below.

<Formula 3>

In the structural formula of Formula 3, * represents a bonding site. In the above structural formula, Z may independently be any one of a single bond, O, S, SO ₂ , CO, and (C=C)n, and n may be an integer of 1 to 5. Although the binding position of Z to each ring is not particularly limited, the binding position of Z may be, for example, an ortho or para position to each ring. The hydrogen atom in the structural formula of Formula 3 is a halogen element; hydrocarbon group; a halogen-substituted hydrocarbon group; Alternatively, it may be substituted by a halogen element, an oxygen or nitrogen substituted hydrocarbon group. In Formula 3, each structural formula may be a heterocyclic organic group in which at least one carbon in the structural formula is substituted with an element such as nitrogen (N), sulfur (S), or oxygen (O).

According to one embodiment of the present invention, the UV absorber may include Tetraethyl 2,2'-(1,4-phenylenedimethylidyne)bismalonate.

According to one embodiment of the present invention, the light-transmitting substrate may include 1 to 10 parts by weight of the ultraviolet absorber based on 100 parts by weight of the polymer resin.

When less than 1 part by weight of the ultraviolet absorber is included with respect to 100 parts by weight of the polymer resin, the effect of improving light fastness is insignificant, so that the color change (ΔE* _ab ) exceeds 3.5 after the light fastness test. Conversely, when more than 10 parts by weight of the ultraviolet absorber is included with respect to 100 parts by weight of the polymer resin, the initial yellowness before the light resistance test exceeds 5.0, and dissolution problems may occur during long-term storage.

According to one embodiment of the present invention, the optical film 101 may further include a primer layer 120 on the light-transmitting substrate 110 . 2 is a cross-sectional view of the optical film 101 further including a primer layer 120.

As shown in FIG. 2 , the optical film 101 further including the primer layer 120 may be stacked with the light transmissive substrate 110 and the primer layer 120 in that order.

The primer layer 120 of the present invention may include a curable resin. According to one embodiment of the present invention, the curable resin may include at least one selected from acrylic resins, urethane-based resins, and siloxane-based resins.

According to one embodiment of the present invention, the primer layer 120 of the present invention includes a UV absorber; and pigments; At least one of them may be further included.

According to one embodiment of the present invention, the primer layer 120 may include the same malonate ultraviolet absorber as the light-transmitting substrate 110, or other ultraviolet rays other than the malonate ultraviolet absorber. An absorbent may also be included. The present invention is not limited thereto.

According to one embodiment of the present invention, the pigment may include a copper-phthalocyanine (Cu-phthalocyanine)-based compound. However, the present invention is not limited thereto, and other pigments may be used in addition to the copper-phthalocyanine-based compound.

According to one embodiment of the present invention, the primer layer 120 may have a thickness of 0.1 to 10 μm. Preferably, the primer layer 120 may have a thickness of 1 to 5 μm. However, the present invention is not limited thereto.

According to an embodiment of the present invention, the optical film 102 may further include a hard coating layer 130 on the light transmissive substrate 110 . 3 is a cross-sectional view of the optical film 102 further including a hard coat layer 130.

As shown in FIG. 3 , the optical film 102 further including the hard coating layer 130 may be laminated in the order of the light-transmitting substrate 110 and the hard coating layer 130 .

The hard coating layer 130 is a layer that protects the adherend to which the optical film 102 and the optical film 101 are attached from the external environment. According to an embodiment of the present invention, the hard coating layer 130 is a siloxane-based resin. , It may include at least one of an acrylic resin, a urethane-based resin, and an epoxy-based resin.

According to one embodiment of the present invention, the hard coating layer 130 may have a thickness of 1 to 10 μm, preferably, a thickness of 1 to 5 μm. However, the present invention is not limited thereto.

*84 According to one embodiment of the present invention, the optical film may include both the primer layer 120 and the hard coating layer 130 on top of the light transmissive substrate 110 (the drawing is omitted). The optical film further including the primer layer 120 and the hard coat layer 130 may be stacked in the order of the light transmissive substrate 110 , the primer layer 120 , and the hard coat layer 130 .

According to one embodiment of the present invention, the optical film 100 may have light transmissive and flexible characteristics. For example, an optical film according to an embodiment of the present invention may have bending characteristics, folding characteristics, and rollable characteristics.

According to an embodiment of the present invention, the optical film 100 may have a light transmittance of 88.5% or more before the light fastness test, and a haze of 0.4 or less before the light fastness test.

The light transmittance before the light fastness test was measured using a spectrophotometer according to the standard ASTM E313, for example, a spectrophotometer manufactured by KONICA MINOLTA (model name: CM-3700D), and the average light transmittance in the wavelength range of 360 to 740 nm. can measure

The haze before the light fastness test was measured by cutting the manufactured optical film 100 into 50 mm x 50 mm and using a haze meter according to the standard ASTM D1003, for example, a haze meter manufactured by MURAKAMI (model name: HM-150), It is measured three times, and the average value of the three measured values can be used as the haze value.

According to an embodiment of the present invention, the optical film 100 may have a light transmittance of 88.5% or more after the light fastness test, and a haze of 1.0 or less after the light fastness test.

The light transmittance and haze after the light fastness test may be measured by the same method as the light transmittance and haze measurement method before the light fastness test.

The optical film 100 according to an embodiment of the present invention may be applied to a display device to protect a display surface of a display panel. The optical film 100 according to an embodiment of the present invention may have a thickness sufficient to protect the display panel. For example, the optical film 100 may have a thickness of 20 μm to 120 μm. However, the present invention is not limited thereto.

Hereinafter, a display device using the optical film 100 according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5 .

FIG. 4 is a cross-sectional view of a part of a display device 200 according to another embodiment of the present invention, and FIG. 5 is an enlarged cross-sectional view of part “P” in FIG. 4 .

Referring to FIG. 4 , a display device 200 according to another embodiment of the present invention includes a display panel 501 and an optical film 100 on the display panel 501 . The optical film 100 of FIG. 4 may be the optical film 101 of FIG. 2 or the optical film 102 of FIG. 3 .

Referring to FIGS. 4 and 5 , the display panel 501 includes a substrate 510 , a thin film transistor (TFT) on the substrate 510 , and an organic light emitting device 570 connected to the thin film transistor (TFT). The organic light emitting device 570 includes a first electrode 571 , an organic light emitting layer 572 on the first electrode 571 , and a second electrode 573 on the organic light emitting layer 572 . The display device 200 illustrated in FIGS. 4 and 5 is an organic light emitting display device.

Substrate 510 may be made of glass or plastic. Specifically, the substrate 510 may be made of plastic such as polyimide-based resin. Although not shown, a buffer layer may be disposed on the substrate 510 .

A thin film transistor (TFT) is disposed on the substrate 510 . The thin film transistor (TFT) includes a semiconductor layer 520, a gate electrode 530 insulated from the semiconductor layer 520 and overlapping at least a portion of the semiconductor layer 520, a source electrode 541 connected to the semiconductor layer 520, and A drain electrode 542 spaced apart from the source electrode 541 and connected to the semiconductor layer 520 is included.

Referring to FIG. 5 , a gate insulating layer 535 is disposed between the gate electrode 530 and the semiconductor layer 520 . An interlayer insulating layer 551 may be disposed on the gate electrode 530 , and a source electrode 541 and a drain electrode 542 may be disposed on the interlayer insulating layer 551 .

The planarization layer 552 is disposed on the thin film transistor TFT to planarize an upper portion of the thin film transistor TFT.

The first electrode 571 is disposed on the planarization layer 552 . The first electrode 571 is connected to the thin film transistor TFT through a contact hole provided in the planarization layer 552 .

The bank layer 580 is disposed on a portion of the first electrode 571 and the planarization layer 552 to define a pixel area or light emitting area. For example, since the bank layer 580 is arranged in a matrix structure in a boundary area between a plurality of pixels, a pixel area may be defined by the bank layer 580 .

An organic emission layer 572 is disposed on the first electrode 571 . The organic emission layer 572 may also be disposed on the bank layer 580 . The organic light emitting layer 572 may include one light emitting layer or may include two or more light emitting layers stacked on top and bottom. Light having one of red, green, and blue colors may be emitted from the organic emission layer 572, and white light may also be emitted.

The second electrode 573 is disposed on the organic light emitting layer 572 .

The organic light emitting element 570 may be formed by stacking the first electrode 571 , the organic light emitting layer 572 , and the second electrode 573 .

Although not shown, when the organic light emitting layer 572 emits white light, each pixel may include a color filter for filtering white light emitted from the organic light emitting layer 572 for each wavelength. A color filter is formed on the light movement path.

A thin film encapsulation layer 590 may be disposed on the second electrode 573 . The thin film encapsulation layer 590 may include at least one organic layer and at least one inorganic layer, and at least one organic layer and at least one inorganic layer may be alternately disposed.

The optical film 100 is disposed on the display panel 501 having the above-described laminated structure.

Hereinafter, the present invention will be described in more detail with reference to illustrative examples and comparative examples. However, the present invention is not limited by the Examples and Comparative Examples described below.

<Preparation Example: Polymer Resin Preparation>

After filling 776.655 g of DMAc (N,N-Dimethylacetamide) while passing nitrogen through a 1L reactor equipped with an agitator, nitrogen injector, dropping funnel, temperature controller and cooler, adjust the temperature of the reactor to 25 ^o C, and then set the temperature of the reactor to TFDB (Bis(trifluoromethyl)benzidine) 54.439 g (0.17 mol) was dissolved and the solution was maintained at 25 ^o C. 15.005 g (0.051 mol) of BPDA (biphenyl-tetracarboxylic acid dianhydride) was added and stirred for 3 hours to completely dissolve BPDA, followed by 6FDA (4,4'-(Hexafluoroisopropylidene) diphthalic anhydride) 22.657 g (0.051 mol) was added to dissolve completely. After lowering the temperature of the reactor to 10 ^° C, 13.805 g (0.068 mol) of TPC (Terephthaloyl chloride) was added and reacted at 25 ^° C for 12 hours to obtain a polymer solution having a solid concentration of 12% by weight.

17.75 g of pyridine and 22.92 g of acetic anhydride were added to the obtained polymer solution, stirred for 30 minutes, stirred at 70 ^° C for 1 hour, cooled to room temperature, and 20 L of methanol was added to the obtained polymer solution to precipitate solids, The precipitated solid content was filtered and pulverized, washed again with 2 L of methanol, and then dried in a vacuum at 100 ^° C. for 6 hours to obtain a powdery polyimide-based polymer solid content. The polyimide-based polymer solid content prepared here is a polyamide-imide polymer solid content.

<Example 1>

In a 500mL reactor, 300 parts by weight of DMAc and 2 parts by weight of Tetraethyl 2,2'-(1,4-phenylenedimethylidyne)bismalonate (ultraviolet absorber, Cas No.: 6337-43-5, Campia's Eversorb 320) was added, and after sufficiently dissolving at room temperature for 10 minutes, the mixture was stirred while maintaining the temperature of the reactor at 5 ^° C. Thereafter, 43.72 parts by weight of the polyimide-based polymer solid powder prepared in Preparation Example was added, stirred for 1 hour, and heated to 25 ^° C. to prepare a liquid polyimide-based resin solution. The maximum absorbance of tetraethyl 2,2'-(1,4-phenylenedimethylidyne)bismalonate was 0.95 (@321nm).

The obtained polyimide-based resin solution was applied to a casting substrate and cast, and dried with hot air at 130 ^° C for 30 minutes to prepare a film, and then the prepared film was peeled from the casting substrate and fixed to a frame with pins. At this time, there is no particular limitation on the type of casting substrate. As the casting substrate, a glass substrate, a stainless (SUS) substrate, a Teflon substrate, or the like may be used. In Example 1, an organic substrate was used as a casting substrate. the same below

The frame on which the film was fixed was placed in a vacuum oven, heated slowly from 100 ^° C to 280 ^° C for 2 hours, and then slowly cooled and separated from the frame to obtain a polyimide-based optical film. Again, the polyimide-based optical film was heat treated at 250 ^° C. for 5 minutes. As a result, a polyimide-based optical film having a thickness of 50 μm was completed.

<Example 2>

In the same manner as in Example 1, the optical film of Example 2 was prepared by varying the content of the ultraviolet absorber.

The content of the specific UV absorber of Example 2 is shown in Table 1 below.

<Comparative Examples 1 to 4>

Optical films of Comparative Examples 1 to 4 were prepared in the same manner as in Example 1, by changing the type and content of the UV absorber.

The types and contents of specific UV absorbers of Comparative Examples 1 to 4 are shown in Table 1 below.

At this time, the maximum absorbance of the UVA region (315 to 400 nm) of the UV absorber was measured by dissolving each UV absorber in DMAc at 0.001 wt%, and then measuring the UVA region (315-400 nm) using Shimadzu's UV spectrophotometer UV-1800. The absorbance was measured, and the maximum value among the absorbances measured in the UVA range (315 to 400 nm) was set as the maximum absorbance in the UVA range (315 to 400 nm) of the UV absorber.

division	UV absorber	Maximum absorbance in the UVA region of the UV absorber	Polyimide-based polymer solid content (parts by weight)	Content of UV absorber (parts by weight)	thickness (μm)
Example 1	Tetraethyl 2,2'-(1,4-phenylenedimethylidyne)bismalonate	0.95 (@321nm)	100	2	50
Example 2	Tetraethyl 2,2'-(1,4-phenylenedimethylidyne)bismalonate	0.95 (@321nm)	100	4	50
Comparative Example 1	-	-	100	0	50
Comparative Example 2	2Phenol,2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)	0.32 (@333nm)	100	3	50
Comparative Example 3	2Phenol,2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)	0.32 (@333nm)	100	4	50
Comparative Example 4	Phenol,2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methyl	0.43 (@349nm)	100	One	50

<Measurement Example> The following measurements were performed on the optical films prepared in Examples 1 to 2 and Comparative Examples 1 to 4. The following measurement examples were measured before the light fastness test and again after the light fastness test.

The light fastness test is performed using a Xenon lamp, specifically, ATLAS' SUNTEST XXL+ device, Daylight filter, 12kW 0.8W/㎡ @420nm, 30 ^o C/30RH% Chamber, 55 ^o C Black Panel conditions was carried out for 300 hours.

1) Yellowness (Y.I.)

Yellowness was measured using a spectrophotometer. Specifically, the yellowness of the optical film was measured using a spectrophotometer, for example, a spectrophotometer manufactured by KONICA MINOLTA (model name: CM-3700D) according to standard ASTM E313.

2) L*, a*, b* and color change (ΔE* _ab )

The color change (ΔE* _ab ) of the optical films prepared according to Examples and Comparative Examples was calculated by Equation 1 below.

<Formula 1>

ΔE* _ab = [(ΔL*) ² + (Δa*) ² + (Δb*) ² ] ^½

In Equation 1, ΔL* is the L* difference before and after the light fastness test, Δa* is the a* difference before and after the light fastness test, and Δb* is the b* difference before and after the light fastness test.

Before the light resistance test of the optical film 100, L*, a*, and b* were measured using a color difference meter. Specifically, the optical film 100 was measured using a color difference meter, for example, KONICA MINOLTA's color difference meter (model name: CM-3600A), using a D65 light source, viewing angle of 2 °, and L*, a*, b* in transmission mode. is measured three times, respectively, and average values of L*, a*, and b* measured three times are calculated to be L*, a*, and b* of the optical film 100. After the light fastness test, L*, a*, and b* were measured by the same method as the L*, a*, b* measurement method before the light fastness test.

3) Light transmittance

The optical films prepared according to Examples and Comparative Examples were measured using a spectrophotometer according to the standard ASTM E313, for example, a spectrophotometer manufactured by KONICA MINOLTA (model name: CM-3700D) in the wavelength range of 360 to 740 nm. The average light transmittance at was measured.

4) Haze

The optical films prepared according to Examples and Comparative Examples were cut into 50 mm x 50 mm and measured 5 times using a haze meter according to the standard ASTM D1003, for example, a haze meter manufactured by MURAKAMI (model name: HM-150). It was measured, and the average value of 5 measurements was taken as the haze value of the optical film.

The measurement results are shown in Tables 2 and 3 below.

division	Before light fastness test
	Y.I.	L*(D65)	a*(D65)	b*(D65)	light transmittance	haze
Example 1	2.9	95.6	-0.7	2.3	89.0	0.2
Example 2	3.3	95.6	-0.8	2.5	89.0	0.2
Comparative Example 1	2.6	95.6	-0.7	2.1	89.1	0.1
Comparative Example 2	3.3	95.6	-0.9	2.6	88.9	0.2
Comparative Example 3	3.4	95.6	-1.0	2.7	89.0	0.1
Comparative Example 4	5.1	95.5	-1.1	3.2	88.9	0.2

division	After light fastness test
	Y.I.	L*(D65)	a*(D65)	b*(D65)	light transmittance	haze	ΔE* ab
Example 1	7.8	95.8	-1.7	5.7	89.5	0.7	3.5
Example 2	7.1	95.8	-1.5	5.1	89.6	0.7	2.7
Comparative Example 1	9.0	95.7	-1.9	6.5	89.2	0.8	4.6
Comparative Example 2	8.8	95.7	-1.9	6.4	89.4	0.8	3.9
Comparative Example 3	8.9	95.7	-1.9	6.5	89.3	0.7	3.9
Comparative Example 4	9.5	95.6	-2.1	7.0	89.1	1.1	3.9

As disclosed in the measurement results of Tables 2 and 3, the optical films of Examples 1 and 2 of the present invention all had a yellowness of 5.0 or less before the light fastness test, a yellowness of 7.8 or less after the light fastness test, and a light transmittance of 88.5%. Above, the haze was 1.0 or less, and ΔE* _ab was 3.5 or less. However, looking at the optical films of Comparative Examples 1 to 4, Comparative Examples 1 to 3 had a ΔE* _ab of more than 3.5 after the light fastness test, indicating that the optical film It was confirmed that the visibility decreased due to the decrease in color reproducibility and sharpness. Comparative Example 4 had an initial yellowness of more than 5.0 before the light fastness test, haze after the light fastness test of more than 1.0, and a ΔE* _ab of more than 3.5, showing high initial yellowness of the optical film, color reproducibility of the optical film after the light fastness test, and It was confirmed that the visibility decreased due to the decrease in sharpness.

The features, structures, effects, etc. illustrated in each of the above-described embodiments can be combined or modified with respect to other embodiments by those skilled in the art in the field to which the embodiments belong. Therefore, contents related to these combinations and variations should be construed as being included in the scope of the present invention.

Claims (9)

1. Including a light-transmitting substrate,

   The yellowness before the light fastness test is 5.0 or less,

   After the light fastness test, the color change (ΔE* _ab ) is 3.5 or less,

   Optical film:

   The light resistance test was conducted for 300 hours under the conditions of a Daylight filter, 12kW 0.8W/m2 @420nm, 30 ^o C/30RH% Chamber, and 55 ^o C Black Panel using a Xenon lamp,

   The color change (ΔE* _ab ) is calculated by Equation 1 below.

   <Formula 1>

   ΔE* _ab = [(ΔL*) ² + (Δa*) ² +(Δb*) ² ] ^1/2

   In Equation 1, ΔL* is the L* difference before and after the light fastness test, Δa* is the a* difference before and after the light fastness test, and Δb* is the b* difference before and after the light fastness test.
2. According to claim 1,

   The light-transmitting substrate,

   polymer resin; and

   Malonate-based (Malonate) UV absorber; containing,

   optical film.
3. According to claim 2,

   The ultraviolet absorber has a maximum absorbance of 0.45 or more in the UVA region (315 to 400 nm) when dissolved in DAMc at a concentration of 0.001 wt%.

   optical film.
4. According to claim 2,

   The ultraviolet absorber includes a compound represented by Formula 2 below,

   Optical film:

   <Formula 2>

   

   In Formula 2, R ¹ , R ² , R ³ and R ⁴ are each independently hydrogen; halogen element; phenyl group; Or a C1~C10 linear, branched or alicyclic alkyl group; Y is a divalent aromatic or heteroorganic group having 6 to 40 carbon atoms, and a hydrogen atom in the organic group included in Formula 2 is a halogen element; hydrocarbon group; a halogen-substituted hydrocarbon group; Alternatively, it may be substituted by a halogen element, an oxygen or nitrogen substituted hydrocarbon group.
5. According to claim 2,

   The ultraviolet absorber includes Tetraethyl 2,2'-(1,4-phenylenedimethylidyne)bismalonate,

   optical film.
6. According to claim 2,

   The light-transmitting substrate includes 1 to 10 parts by weight of the ultraviolet absorber based on 100 parts by weight of the polymer resin.

   optical film.
7. According to claim 2,

   The polymer resin includes at least one or more of an imide repeating unit and an amide repeating unit.

   optical film.
8. According to claim 1,

   After the light fastness test, the light transmittance is 88.5% or more,

   Haze is less than 1.0 after light fastness test,

   optical film.
9. display panel; and

   An optical film of any one of claims 1 to 8 disposed on the display panel;

   display device.

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